<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <meta http-equiv="X-UA-Compatible" content="IE=edge">
    <meta name="viewport" content="width=device-width, initial-scale=1.0">
    <title>Document</title>
    <style>
        div{
            width: 200px;
            height: 200px;
            font-size: 30px;
        }
        .box1{
            background: red;
        }
        .box2{
            background: blue;
        }
        .box3{
            background: yellow;
        }
    </style>
</head>
<body>
    <div class="container">
        <button class="btn">按钮一</button>
        <button class="btn">按钮二</button>
        <button class="btn">按钮三</button>
        <div class="box1">1</div>
        <div class="box2">2</div>
        <div class="box3">3</div>
    </div>
    <script>

        // 一、一个选项卡 ；
        var btns = document.querySelectorAll(".btn");
        var divs = document.querySelectorAll(".container div");
        btns.forEach((btn,k)=>{
            btn.onclick = function(){
                console.log(k);
                divs.forEach((div,key)=>{
                    if(key==k){
                        div.style.display = "block";
                    }else{
                        div.style.display = "none";
                    }
                })


            }
        })




    </script>
</body>
</html>